Influence of Texture on the Fracture Toughness of Unirradiated Zircaloy Cladding

Abstract

The correlation between texture and fracture toughness of the cladding has been investigated in connection with axial cracks in fuel rods. The effect of texture might be expected from the influence of texture on the anisotropy of contractile deformations which, in turn, is expected to modify the stress-strain conditions at the crack tip, and, consequently, alter the crack propagation resistance of the cladding. Stress-relieved and recrystallized Zircaloy-2 cladding with known texture parameters were tested under uniaxial tension in the axial and circumferential directions. The anisotropy of contractile deformation in uniaxial tests was characterized by means of Hill's parameters F, G, and H. The fracture toughness of the cladding was evaluated by means of the pin-loading tension test. An influence of texture on the fracture toughness has been found for as-received cladding. A higher fracture toughness, i.e., higher resistance to an axial crack propagation, was observed for the cladding with more radial texture. No significant effect of the test temperature on the anisotropy constants F, G, and H has been observed between 293 and 573 K. The parameters F, G, and H are only slightly affected at 573 K by a hydrogen concentration of about 500 wt ppm. More data are needed to draw conclusions about the effect of texture in hydrided cladding.